Roll skia to 8cc209111876b7c78b5ec577c9221d8ed5e21024

skia/ext/convolver.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SKIA_EXT_CONVOLVER_H_
+#define SKIA_EXT_CONVOLVER_H_
+
+#include <cmath>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "third_party/skia/include/core/SkSize.h"
+#include "third_party/skia/include/core/SkTypes.h"
+
+// We can build SSE2 optimized versions for all x86 CPUs
+// except when building for the IOS emulator.
+#if defined(ARCH_CPU_X86_FAMILY) && !defined(OS_IOS)
+#define SIMD_SSE2 1
+#define SIMD_PADDING 8  // 8 * int16
+#endif
+
+#if defined(ARCH_CPU_MIPS_FAMILY) && defined(__mips_dsp) && \
+    (__mips_dsp_rev >= 2)
+#define SIMD_MIPS_DSPR2 1
+#endif
+// avoid confusion with Mac OS X's math library (Carbon)
+#if defined(__APPLE__)
+#undef FloatToFixed
+#undef FixedToFloat
+#endif
+
+namespace skia {
+
+// Represents a filter in one dimension. Each output pixel has one entry in this
+// object for the filter values contributing to it. You build up the filter
+// list by calling AddFilter for each output pixel (in order).
+//
+// We do 2-dimensional convolution by first convolving each row by one
+// ConvolutionFilter1D, then convolving each column by another one.
+//
+// Entries are stored in fixed point, shifted left by kShiftBits.
+class ConvolutionFilter1D {
+ public:
+  typedef short Fixed;
+
+  // The number of bits that fixed point values are shifted by.
+  enum { kShiftBits = 14 };
+
+  SK_API ConvolutionFilter1D();
+  SK_API ~ConvolutionFilter1D();
+
+  // Convert between floating point and our fixed point representation.
+  static Fixed FloatToFixed(float f) {
+    return static_cast<Fixed>(f * (1 << kShiftBits));
+  }
+  static unsigned char FixedToChar(Fixed x) {
+    return static_cast<unsigned char>(x >> kShiftBits);
+  }
+  static float FixedToFloat(Fixed x) {
+    // The cast relies on Fixed being a short, implying that on
+    // the platforms we care about all (16) bits will fit into
+    // the mantissa of a (32-bit) float.
+    static_assert(sizeof(Fixed) == 2,
+                  "fixed type should fit in float mantissa");
+    float raw = static_cast<float>(x);
+    return ldexpf(raw, -kShiftBits);
+  }
+
+  // Returns the maximum pixel span of a filter.
+  int max_filter() const { return max_filter_; }
+
+  // Returns the number of filters in this filter. This is the dimension of the
+  // output image.
+  int num_values() const { return static_cast<int>(filters_.size()); }
+
+  // Appends the given list of scaling values for generating a given output
+  // pixel. |filter_offset| is the distance from the edge of the image to where
+  // the scaling factors start. The scaling factors apply to the source pixels
+  // starting from this position, and going for the next |filter_length| pixels.
+  //
+  // You will probably want to make sure your input is normalized (that is,
+  // all entries in |filter_values| sub to one) to prevent affecting the overall
+  // brighness of the image.
+  //
+  // The filter_length must be > 0.
+  //
+  // This version will automatically convert your input to fixed point.
+  SK_API void AddFilter(int filter_offset,
+                        const float* filter_values,
+                        int filter_length);
+
+  // Same as the above version, but the input is already fixed point.
+  void AddFilter(int filter_offset,
+                 const Fixed* filter_values,
+                 int filter_length);
+
+  // Retrieves a filter for the given |value_offset|, a position in the output
+  // image in the direction we're convolving. The offset and length of the
+  // filter values are put into the corresponding out arguments (see AddFilter
+  // above for what these mean), and a pointer to the first scaling factor is
+  // returned. There will be |filter_length| values in this array.
+  inline const Fixed* FilterForValue(int value_offset,
+                                     int* filter_offset,
+                                     int* filter_length) const {
+    const FilterInstance& filter = filters_[value_offset];
+    *filter_offset = filter.offset;
+    *filter_length = filter.trimmed_length;
+    if (filter.trimmed_length == 0) {
+      return NULL;
+    }
+    return &filter_values_[filter.data_location];
+  }
+
+  // Retrieves the filter for the offset 0, presumed to be the one and only.
+  // The offset and length of the filter values are put into the corresponding
+  // out arguments (see AddFilter). Note that |filter_legth| and
+  // |specified_filter_length| may be different if leading/trailing zeros of the
+  // original floating point form were clipped.
+  // There will be |filter_length| values in the return array.
+  // Returns NULL if the filter is 0-length (for instance when all floating
+  // point values passed to AddFilter were clipped to 0).
+  SK_API const Fixed* GetSingleFilter(int* specified_filter_length,
+                                      int* filter_offset,
+                                      int* filter_length) const;
+
+  inline void PaddingForSIMD() {
+// Padding |padding_count| of more dummy coefficients after the coefficients
+// of last filter to prevent SIMD instructions which load 8 or 16 bytes
+// together to access invalid memory areas. We are not trying to align the
+// coefficients right now due to the opaqueness of <vector> implementation.
+// This has to be done after all |AddFilter| calls.
+#ifdef SIMD_PADDING
+    for (int i = 0; i < SIMD_PADDING; ++i)
+      filter_values_.push_back(static_cast<Fixed>(0));
+#endif
+  }
+
+ private:
+  struct FilterInstance {
+    // Offset within filter_values for this instance of the filter.
+    int data_location;
+
+    // Distance from the left of the filter to the center. IN PIXELS
+    int offset;
+
+    // Number of values in this filter instance.
+    int trimmed_length;
+
+    // Filter length as specified. Note that this may be different from
+    // 'trimmed_length' if leading/trailing zeros of the original floating
+    // point form were clipped differently on each tail.
+    int length;
+  };
+
+  // Stores the information for each filter added to this class.
+  std::vector<FilterInstance> filters_;
+
+  // We store all the filter values in this flat list, indexed by
+  // |FilterInstance.data_location| to avoid the mallocs required for storing
+  // each one separately.
+  std::vector<Fixed> filter_values_;
+
+  // The maximum size of any filter we've added.
+  int max_filter_;
+};
+
+// Does a two-dimensional convolution on the given source image.
+//
+// It is assumed the source pixel offsets referenced in the input filters
+// reference only valid pixels, so the source image size is not required. Each
+// row of the source image starts |source_byte_row_stride| after the previous
+// one (this allows you to have rows with some padding at the end).
+//
+// The result will be put into the given output buffer. The destination image
+// size will be xfilter.num_values() * yfilter.num_values() pixels. It will be
+// in rows of exactly xfilter.num_values() * 4 bytes.
+//
+// |source_has_alpha| is a hint that allows us to avoid doing computations on
+// the alpha channel if the image is opaque. If you don't know, set this to
+// true and it will work properly, but setting this to false will be a few
+// percent faster if you know the image is opaque.
+//
+// The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order
+// (this is ARGB when loaded into 32-bit words on a little-endian machine).
+SK_API void BGRAConvolve2D(const unsigned char* source_data,
+                           int source_byte_row_stride,
+                           bool source_has_alpha,
+                           const ConvolutionFilter1D& xfilter,
+                           const ConvolutionFilter1D& yfilter,
+                           int output_byte_row_stride,
+                           unsigned char* output,
+                           bool use_simd_if_possible);
+
+// Does a 1D convolution of the given source image along the X dimension on
+// a single channel of the bitmap.
+//
+// The function uses the same convolution kernel for each pixel. That kernel
+// must be added to |filter| at offset 0. This is a most straightforward
+// implementation of convolution, intended chiefly for development purposes.
+SK_API void SingleChannelConvolveX1D(const unsigned char* source_data,
+                                     int source_byte_row_stride,
+                                     int input_channel_index,
+                                     int input_channel_count,
+                                     const ConvolutionFilter1D& filter,
+                                     const SkISize& image_size,
+                                     unsigned char* output,
+                                     int output_byte_row_stride,
+                                     int output_channel_index,
+                                     int output_channel_count,
+                                     bool absolute_values);
+
+// Does a 1D convolution of the given source image along the Y dimension on
+// a single channel of the bitmap.
+SK_API void SingleChannelConvolveY1D(const unsigned char* source_data,
+                                     int source_byte_row_stride,
+                                     int input_channel_index,
+                                     int input_channel_count,
+                                     const ConvolutionFilter1D& filter,
+                                     const SkISize& image_size,
+                                     unsigned char* output,
+                                     int output_byte_row_stride,
+                                     int output_channel_index,
+                                     int output_channel_count,
+                                     bool absolute_values);
+
+// Set up the |filter| instance with a gaussian kernel. |kernel_sigma| is the
+// parameter of gaussian. If |derivative| is true, the kernel will be that of
+// the first derivative. Intended for use with the two routines above.
+SK_API void SetUpGaussianConvolutionKernel(ConvolutionFilter1D* filter,
+                                           float kernel_sigma,
+                                           bool derivative);
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_CONVOLVER_H_